Does this help?
-- firstly, for test purposes, build a table of delivery dates in required format
create table #temp ( mydate varchar(50));
declare @d date;
set @d = '20200101';
declare @s char(10);
while @d <= cast(getdate() as date)
begin
set @s = convert(varchar(50), @d, 103);
insert into #temp values (@s);
set @d = dateadd(d,1,@d);
end
-- check character dates are in format required
select mydate from #temp;
-- check expression
select dateadd(day,-199,cast(getdate() as date));
-- check where clause
select mydate from #temp
where mydate between convert(varchar(50),dateadd(day,-199,cast(getdate() as date)),103)
and cast(getdate() as date) ;